Hello , i use 12.04 64bit and 12.10 32 bit and i have no delays.
I have 2 kalendars on one network and rainlendar starts within 2 seconds,guesing the most time to get the calendar from the net.And yes rainlendar is awsome.

As far as I cansee, if we feed Rainlendar with more then certain number of events/ToDo-s, it starts to take your lifetime and eat it...
No matter what I do, I have to avoid to click OK in any ToDo window.
If I click OK, I need to be prepared to go take a shower os something like that...
...it's a really cool software but this is a HUGE issue that should be considered, don't you agree?
How many events and task do you have? I tried with 10000 events and the startup takes about 3 seconds and the event dialog closes in about 1 seconds after the OK button is clicked. It would help if you provided the debug log so I could check what exactly is happening when you edit an event.